Add Force stereo for 2SID setting (#18)

Author: sandlbn

src/config.rs

@@ -31,6 +31,9 @@ pub struct Config {
     pub last_songlength_file: Option<String>,
     /// Last directory used for playlists.
     pub last_playlist_dir: Option<String>,
+    /// Force stereo mirroring for 2SID tunes (duplicate SID1 writes to SID2).
+    /// When enabled, 2SID tunes play in mono-stereo mode instead of true dual-SID.
+    pub force_stereo_2sid: bool,
 }
 
 impl Default for Config {
@@ -46,6 +49,7 @@ impl Default for Config {
             last_songlength_dir: None,
             last_songlength_file: None,
             last_playlist_dir: None,
+            force_stereo_2sid: false,
         }
     }
 }
@@ -155,6 +159,9 @@ impl Config {
                 if val != "null" {
                     config.last_playlist_dir = strip_json_string(val);
                 }
+            } else if let Some(rest) = line.strip_prefix("\"force_stereo_2sid\"") {
+                let val = rest.trim().trim_start_matches(':').trim();
+                config.force_stereo_2sid = val == "true";
             }
         }
 
@@ -181,7 +188,8 @@ impl Config {
                 "  \"last_sid_dir\": {},\n",
                 "  \"last_songlength_dir\": {},\n",
                 "  \"last_songlength_file\": {},\n",
-                "  \"last_playlist_dir\": {}\n",
+                "  \"last_playlist_dir\": {},\n",
+                "  \"force_stereo_2sid\": {}\n",
                 "}}\n",
             ),
             self.skip_rsid,
@@ -194,6 +202,7 @@ impl Config {
             fmt_opt(&self.last_songlength_dir),
             fmt_opt(&self.last_songlength_file),
             fmt_opt(&self.last_playlist_dir),
+            self.force_stereo_2sid,
         )
     }
 

src/main.rs

@@ -612,6 +612,11 @@ impl App {
                 self.config.save();
             }
 
+            Message::ToggleForceStereo2sid => {
+                self.config.force_stereo_2sid = !self.config.force_stereo_2sid;
+                self.config.save();
+            }
+
             Message::DefaultSongLengthChanged(val) => {
                 self.default_length_text = val.clone();
                 // Parse and apply the value
@@ -965,7 +970,8 @@ impl App {
             self.selected = Some(idx);
             self.scroll_to_current = true;
 
-            let force_stereo = std::env::args().any(|a| a == "--stereo");
+            let force_stereo =
+                self.config.force_stereo_2sid || std::env::args().any(|a| a == "--stereo");
             let sid4_addr = parse_sid4_from_args();
 
             let _ = self.cmd_tx.send(PlayerCmd::Play {

src/player/mod.rs

@@ -726,7 +726,7 @@ fn setup_playback(
     sid_file: SidFile,
     path: PathBuf,
     song: u16,
-    _force_stereo: bool,
+    force_stereo: bool,
     sid4_addr: u16,
     is_rsid: bool,
     bridge: &mut Option<Box<dyn SidDevice>>,
@@ -749,22 +749,35 @@ fn setup_playback(
     // Always use stereo mode — mono tunes get mirrored to both channels
     // so sound comes from both speakers.
     let use_stereo = true;
-    let mono_mode = !is_multi;
-    let mirror_mono = mono_mode; // always mirror single-SID tunes
-
-    let mapper = SidMapper::new(&sid_bases);
+    // force_stereo: treat 2SID tunes as mono (mirror SID1 to both channels,
+    // ignoring the second SID). Only applies to exactly 2-SID tunes;
+    // 3SID/4SID tunes always use their native multi-SID layout.
+    let force_mono_2sid = force_stereo && num_sids == 2;
+    let mono_mode = !is_multi || force_mono_2sid;
+    let mirror_mono = mono_mode; // mirror single-SID tunes (and forced-stereo 2SID)
+
+    // When forcing stereo on a 2SID tune, use only the base SID for mapping
+    let mapper = if force_mono_2sid {
+        SidMapper::new(&sid_bases[..1])
+    } else {
+        SidMapper::new(&sid_bases)
+    };
     let frame_us = header.frame_us();
     let cycles_per_frame = if header.is_pal {
         PAL_CYCLES_PER_FRAME
     } else {
         NTSC_CYCLES_PER_FRAME
     };
 
-    let sid_type = match num_sids {
-        1 => "Mono".to_string(),
-        2 => "2SID Stereo".to_string(),
-        3 => "3SID".to_string(),
-        n => format!("{}SID", n),
+    let sid_type = if force_mono_2sid {
+        "2SID → Stereo (forced mono)".to_string()
+    } else {
+        match num_sids {
+            1 => "Mono".to_string(),
+            2 => "2SID Stereo".to_string(),
+            3 => "3SID".to_string(),
+            n => format!("{}SID", n),
+        }
     };
 
     let md5 = compute_hvsc_md5(&sid_file);

src/ui/mod.rs

@@ -79,6 +79,7 @@ pub enum Message {
     // Settings
     ToggleSettings,
     ToggleSkipRsid,
+    ToggleForceStereo2sid,
     DefaultSongLengthChanged(String),
     SonglengthUrlChanged(String),
     DownloadSonglength,
@@ -1003,6 +1004,30 @@ pub fn settings_panel<'a>(
 
     let rsid_section = column![rsid_label, rsid_toggle, rsid_help].spacing(6);
 
+    // ── Force stereo for 2SID tunes ──────────────────────────────
+    let stereo_2sid_label = text("Force stereo for 2SID tunes:")
+        .size(14)
+        .color(Color::from_rgb(0.75, 0.77, 0.82));
+
+    let stereo_2sid_toggle = tool_button(
+        if config.force_stereo_2sid {
+            "✓ Yes — mirror SID1 to both channels"
+        } else {
+            "✗ No — true dual-SID (L=SID1, R=SID2)"
+        },
+        Message::ToggleForceStereo2sid,
+    );
+
+    let stereo_2sid_help = text(
+        "When enabled, 2SID tunes ignore the second SID and mirror SID1 to both speakers \
+         (same as mono). Disable for true stereo separation on dual-SID hardware.",
+    )
+    .size(11)
+    .color(Color::from_rgb(0.45, 0.47, 0.52));
+
+    let stereo_2sid_section =
+        column![stereo_2sid_label, stereo_2sid_toggle, stereo_2sid_help].spacing(6);
+
     // ── Default song length ──────────────────────────────────────
     let length_label = text("Default song length (seconds):")
         .size(14)
@@ -1097,6 +1122,8 @@ pub fn settings_panel<'a>(
         rule::horizontal(1),
         rsid_section,
         rule::horizontal(1),
+        stereo_2sid_section,
+        rule::horizontal(1),
         length_section,
         rule::horizontal(1),
         dl_section,